Remote systems, such as vehicles, have been introduced that include locomotion power derived from electricity received from an energy storage device, such as a battery. For example, hybrid electric vehicles include on-board chargers that use power from vehicle braking and traditional motors to charge the vehicles. Vehicles that are solely electric generally receive the electricity for charging the batteries from other sources. Battery electric vehicles (electric vehicles) are often proposed to be charged through some type of wired alternating current (AC) such as household or commercial AC supply sources. The wired charging connections require cables or other similar connectors that are physically connected to a power supply. Cables and similar connectors may sometimes be inconvenient or cumbersome and have other drawbacks. Wireless power charging systems that are capable of transferring power in free space (e.g., via a wireless field) to be used to charge electric vehicles may overcome some of the deficiencies of wired charging solutions. As such, wireless power charging systems and methods that efficiently and safely transfer power for charging electric vehicles are desirable.
Inductive power transfer (IPT) systems are one means for the wireless transfer of energy. In IPT, a primary (or “base”) power device (e.g., a base pad, wireless power transfer pad, base wireless charging system, or some other wireless power transfer device including a power transfer element (e.g., base power transfer element)) transmits power to a secondary (or “pick-up”) power receiver device (e.g., a vehicle pad, an electric vehicle wireless charging unit, or some other wireless power receiving device including a power transfer element (e.g., vehicle power transfer element)). Each of the transmitter and receiver power devices includes inductors, typically coils or windings of electric current conveying media. An alternating current in the primary inductor produces a fluctuating magnetic field. When the secondary inductor is placed in proximity to the primary inductor, the fluctuating magnetic field induces an electromotive force (EMF) in the secondary inductor, thereby transferring power to the secondary power receiver device. In certain systems, such as large scale car-park deployments, semi-dynamic or dynamic systems, it is possible that individual wireless power transfer pads may be driven separately yet capable of interacting magnetically. This magnetic coupling can cause issues with regulations, operation of primary/ancillary systems, or even cause unnecessary power transfer.